A conventional dryer felt consists of an endless conveyor belt made from a multiple-plane fabric, wherein the various planes can be defined either by different groups of cross machine direction yarns, machine direction yarns or both. The planes, or plies, or layers are united in a binding relationship by a plurality of machine direction yarns. The yarns used to weave the most up-to-date dryer felts are made from synthetic monofilaments such as polyester or polyamide, or synthetic multifilaments, from such materials as polyester, acrylic, polyamide or the aramid fiber group--NOMEX and KEVLAR.
Because some of the synthetic materials are quite expensive, manufacturers are continually seeking to improve dryer felts, both in terms of cost and in terms of dryer felt reliability. Along these lines, it is important in certain dryer felts to maintain low air permeability, and one way of lowering the permeability is to weave more yarns to the inch. This, of course, adds to the cost and weight of the already expensive felts.
In co-pending U.S. Application Ser. No. 932,360 filed Aug. 9, 1978, of which this application is a continuation-in-part, there is disclosed an improved dryer felt which overcomes many of the short comings of the prior art. As disclosed in the co-pending application, the improved dryer felt comprises a plurality of machine direction and cross machine direction yarns interwoven in a binding relationship to provide a multiple-plane fabric having at least a base plane, a top plane and an intermediate plane positioned between the base plane and the top plane. Each of the planes is defined by a different plurality of the cross machine direction yarns. The plurality of the cross machine direction yarns, which define the intermediate plane, are encapsulated yarns so as to provide a soft, bulky intermediate plane. Each of the encapsulated yarns comprises a monofilament core and an encapsulating sheath surrounding the full length of the core. The sheath defines a soft bulky outer surface which, when woven into the fabric, acts to prevent shifting, or migrating of the encapsulated yarns bound into the fabtic by the machine direction yarns. The monofilament core of the encapsulated yarn may comprise either a monofilament fiber, or a bundle of fibers treated with a suitable resin, such as phenolic resin, so that the resin treated bundle acts as a monofilament fiber. The encapsulated yarns reduce permeability while contributing to fabric stability.
Although a fabric made according to the teachings of the co-pending application, exhibit improved strength, stability, and permeability characteristics, it has been found that these characteristics may be further improved by applying the teachings of the present invention.